In preliminary experiments we have grown four human pancreatic carcinomata as xenografts in nude mice and in monolayer culture. Two of these have also been established in artificial capillary culture. The four tumors differ histologically: one is a muco-epidermoid carcinoma, one an anaplastic adenocarcinoma, and two moderately differentiated adenocarcinomata. These four tumors, plus others to be established later will be used as models for studies of chemotherapeutic agents, tumor radiosensitivity, purine analog metabolism and isolation and characterization of tumor products including LAI-antigen. Preliminary data indicate the probable existence of cellular heterogeneity in one of the already established cell lines. This will be investigated by isolating cloned lines of tumor cells whose membranes, surface proteins, electron microscopic appearance, behavior in culture, response to chemotherapeutic agents and to radiation will be examined.